Anaerobic curing compositions comprise polymerizable monomers and their curing effect is achieved through a polymerization mechanism which is inhibited by oxygen. Such anaerobic compositions remain as an unpolymerized liquid as long as adequate contact with oxygen or air is maintained and cure spontaneously to a solid state upon the exclusion of oxygen or air.
The anaerobic curing compositions are useful for locking threaded assemblies, sealing porous and flanged assemblies, and, in particular, bonding adjacent surfaces of metals such as threads of a bolt and a nut.
U.S. Pat. No. 2,628,178 discloses oxygenated polyacrylate monomers showing anaerobic curing properties. However, the compositions containing these monomers require a continuous supply of air through them to prevent their polymerization and solidification during storage.
U.S. Pat. No. 2,898,950 describes anaerobic curing compositions containing unoxygenated polyacrylate monomers which are polymerized rapidly and spontaneously to a solid state in the presence of an organic peroxide catalyst upon the exclusion of air or oxygen therefrom. These compositions possess an adequate shelf-stability without the supply of air as long as adequate contact with air is maintained.
U.S. Pat. No. 3,046,262 teaches anaerobic curing compositions comprising imide and/or formamide as an accelerator. However, while the accelator may promote the curing rate, it also tends to lower the shelf stability.
U.S. Pat. No. 3,218,305 provides anaerobic curing compositions having excellent shelf-stability and being capable of rapidly polymerized which comprise, in admixture, monomers, hydroperoxide catalysts, sulfimides, stabilizers including quinone, and organic amines.
U.S. Pat. No. 4,044,044 discloses the addition of certain organophosphorus ester to anaerobic adhesive and sealant compositions to increase adhesiveness. However, these resulting compositions have several deficiencies including the fact that they require a significantly increased curing time and a high curing temperature in excess of 100.degree. C.
U.S. Pat. No. 4,322,509 suggests that the incorporation of an effective amount of carboxylated nitrile elastomer into an anaerobic composition containing an anaerobically polymerizable material having a terminal ethylenically unsaturated group, a polymerization initiator, an organophosphorus ester and a tertiary dimethylarylamine eliminates the undesired gel formation. However, as more components are added to the anaerobic curing composition, its shelf stability normally becomes deteriorated.